It is known that a polarization sensitive element situated in the resonator of a laser in the path of the generated light results in polarization of the light flux in the resonator and enables the laser to output a polarized beam of light. The difference in absorption between two orthogonally polarized components of the flux in the resonator need be only in the order of 1% to effect almost complete linear polarization of the laser's output beam. For example, a flat mirror disposed to have the light incident upon it at a 45.degree. angle may, in some instances, be adequate to provide the requisite difference in absorption. In a compact laser of the flowing gas type which employs a folded optical resonator, the use of a 45.degree. reflector is undesirable because of space limitations in the resonator, the need to avoid interference with the gas flow, and the relatively high cost of suitable reflectors. Further, the use of a 45.degree. reflector makes it difficult to alter the plane of polarization where flexibility is needed to enable the plane of polarization of the laser's output beam to be easily changed. In lieu of that prior arrangement for polarizing the light generated by a gas laser, it is desired to employ a polarizing device that requires a minimum space in the resonator, is less costly than the 45.degree. reflector arrangement, and permits easy alteration of the plane of polarization.